A typical computer network system includes a digital processor, a main disk for storage and several workstations which are serviced by the digital processor and which share the information stored in the main disk. Each workstation generally includes one or more display and keyboard terminals which enable a user to process and view data retrieved on a selected basis from the main disk. In such workstations the cost of the display hardware and the speed with which images can be loaded from the main storage or an image archive is critical and of prime importance. Nowhere is this more so than in a workstation with many high resolution displays, such as one would find in a medical workstation or other workstation used for diagnostic purposes and in an image processing workstation.
In the transmission of image data from an image archive or an image processor to a display workstation, the speed at which the image is transmitted is of paramount importance. There are generally two solutions that can be addressed to decrease this time. One solution is to increase the bandwidth of the communication channel between the image archive and workstation. A second solution is to compress the data prior to transmission. Data compression, in this context, is only effective if the decompression time is negligible in relation to the time saved to transmit the data. There are two main classes of image compression algorithms, noisy algorithms and exact algorithms. Noisy algorithms are those that produce a small difference between the original image and one that has undergone a compression-decompression cycle. Exact algorithms, are those that leave the image completely unchanged upon being decompressed.
Various arrangements of display hardware and use of various compression schemes have been used to provide optimum image display systems within a computer network assembly but none are problem free, simple or inexpensive.